DUAL FUEL, STAGED AIR, LOW NOx GAS BURNER

ABSTRACT

A dual fuel, staged air, low NOx gas burner. The burner assembly includes an elongated air inlet device having a first open end for introduction of air. A first fuel source conduit delivers a first fuel into the air inlet device to a plurality of axially aligned fuel fingers wherein the fingers are spaced in an annular pattern within the air inlet device. A second fuel source conduit delivers a second fuel into the air inlet device to a castellation arm assembly having a plurality of radially extending castellation arms with troughs therein, wherein the axially aligned fuel fingers are juxtaposed between the radially extending castellation arms.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to an apparatus and a method for a dual fuel source, staged combustion air gas burner which produces a compact, stable flame with ultra low NOx emissions.

2. Prior Art

Various nitrogen oxides (NOx) are produced by burners during combustion. The reaction of nitrogen and oxygen gases in atmospheric air produces NOx during combustion. NOx is known to have negative environmental effects and is regulated by governmental agencies. Creation of NOx is known to be highly temperature dependent and sensitive to the fuel-air mixture.

Various methods and attempts have been made to reduce and minimize NOx. These include recirculating flue gas to further consume and reduce NOx emissions, staging of fuel and staging of air.

An example of a prior attempt to control NOx formation may be seen in Kamal et al. (U.S. Pat. No. 5,957,682) entitled Low NOx Burner Assembly wherein a flame is broken down to flamelets in an effort to improve fuel-air mixing.

Another prior art approach is seen in Knight et al. (U.S. Pat. No. 5,718,573) entitled Flashback Resistant Burner which discloses a burner having a primary fuel source and a secondary fuel source.

Notwithstanding the foregoing, there remains a need for an ultra low NOx gas burner.

There also remains a need for a dual fuel source gas burner wherein the combustion air is staged.

SUMMARY OF THE INVENTION

The present invention is directed to a dual fuel, staged air, low NO_(x) gas burner. A substantially tubular elongated air inlet device with a center axis includes a first open end for introduction of combustion air.

A first fuel source conduit delivers a first fuel into the air inlet device. A plurality of axially aligned fuel fingers are in fluid communication with the first fluid source conduit. The axially aligned fuel fingers are arranged and spaced in an annular pattern in the elongated air inlet device. Each of the axially aligned fingers terminates in a hemispherical nozzle.

A second fuel source conduit delivers a second fuel source into the air inlet device. The second fuel source conduit terminates in a hemispherical nozzle. A castellation arm assembly surrounds the nozzle and is in fluid communication with the second fuel source conduit.

The castellation arm assembly includes a plurality of radially extending castellation arms having open troughs. The castellation arms emanate radially from a center coaxial with the hemispherical nozzle and with the second fuel source conduit.

The radially extending castellation arms having open troughs distribute the second fuel source to provide thorough mixing with combustion air.

Additionally, the radially extending castellation arms separate the first fuel source streams emanating from the first fuel fingers in order to thoroughly mix with the combustion air.

A portion of combustion air passes from the air inlet device through a plurality of tubes or channels which are radially spaced in an annular pattern. Combustion air passing into and through the channels exits at a second end of the air inlet device so that the combustion air is staged to the burner assembly.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a sectional, perspective view of a dual fuel, staged air low NO_(x) gas burner assembly constructed in accordance with the present invention;

FIG. 2 illustrates a top view of the burner assembly of the present invention;

FIG. 3 illustrates a portion of a second fuel source conduit apart from the burner assembly;

FIG. 4 illustrates the second fuel conduit along with a first fuel source conduit apart from the balance of the burner assembly; and

FIG. 5 illustrates a sectional view of a portion of the burner assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments discussed herein are merely illustrative of specific manners in which to make and use the invention and are not to be interpreted as limiting the scope of the instant invention.

While the invention has been described with a certain degree of particularity, it is to be noted that many modifications may be made in the details of the invention's construction and the arrangement of its components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification.

Referring to the drawings in detail, FIG. 1 illustrates a sectional, perspective view of a dual fuel, staged air, low NO_(x) gas burner assembly 10 constructed in accordance with the present invention. FIG. 2 illustrates a top view of the burner assembly 10.

The burner assembly 10 includes an elongated air inlet device 12 which is substantially tubular with a center axis. The air inlet device 12 includes a first open end 14 for introduction of air. Either forced or driven air or atmospheric air may be utilized for combustion air. The elongated air device 12 also includes a second end 16 opposed to the first open end 14, which will be described in detail.

The air inlet device 12 passes through a wall of a process heater 18 or the like so that a flame produced by the burner assembly 10 is delivered to the burner 18.

A first fuel source conduit 20 delivers a first fuel (illustrated by arrow 22) through a wall of the elongated air inlet device and into the air inlet device 12.

A plurality of axially aligned fuel fingers 26 are in fluid communication with the first fuel source conduit 20. The axially aligned fuel fingers 26 are arranged and spaced in an annular pattern which is coaxial with the center axis of the elongated air inlet device 12. The fuel fingers 26 are arranged within the elongated air inlet device 12. The axially aligned fuel fingers 26 are in fluid communication with the first fuel source conduit 20 through a ring manifold 28, which can also be seen in FIGS. 4 and 5. Each of the axially aligned fuel fingers 26 terminates in a hemispherical nozzle 24. Each nozzle 24 has a pair of ports, a primary jet port and a secondary jet port. The primary port is at the axial top of the nozzle 24 and mixes rapidly with combustion air while the secondary port is angled and mixes less rapidly.

As seen in FIGS. 1 and 2, a second fuel source conduit 30 delivers a second fuel source (illustrated by arrow 32) through a wall of the air inlet device 12 and into the elongated air inlet device 12.

FIG. 4 illustrates the second fuel conduit 30 along with the first fuel source conduit 20, the ring manifold 28, and the axially aligned fuel fingers 26, apart from the balance of the burner assembly 10. The second fuel source conduit 30 terminates in a hemispherical nozzle 34.

FIG. 3 illustrates a portion of the second fuel source conduit 30 apart from the burner assembly 10. A castellation arm assembly 36 surrounds the nozzle 34 and is in fluid communication with the second fuel source conduit 30. The castellation arm assembly 36 and a portion of the second fuel source conduit 30 may be seen in FIG. 3.

The castellation arm assembly 36 includes a plurality of radially extending castellation arms 38 having open troughs. The castellation arms 38 emanate radially from a center which is coaxial with the hemispherical nozzle 34 and with the second fuel source conduit 30. The castellation arms 38 terminate within the air inlet device 12 between the second end 16 and the termination of the axially aligned fuel fingers 26.

The radially extending castellation arms 38 having open troughs serve to distribute the second fuel source from the second fuel source conduit 30 to provide thorough mixing with combustion air in the air inlet device 12. Accordingly, the second fuel source fuel is spread for distribution within the air inlet device 12.

Additionally, the castellation arms 38 act to separate the first fuel source stream or streams emanating from the fuel fingers 26. Accordingly, the first fuel source which emanates from the axially aligned fuel fingers 26 in the annular space outside of the castellation arms and outside of the second fuel source conduit thoroughly mixes with the combustion air. In a preferred arrangement, there are an equal number of castellation arms 38 and fuel fingers 26, although other arrangements are possible.

The improved mixing achieved in the present invention provides for a better quality flame and lower NO_(x) formation.

The combustion zone begins at the flat base or bluff body of the troughs of the castellation arms 38 and emanates toward the second end 16 of the inlet device 12. The first fuel source emanating from the nozzles 24 of the first fuel fingers 26 mix with combustion air in the elongated air inlet device in advance of the combustion zone. Accordingly, the first fuel source mixes with combustion air in a pre-mix zone before the combustion zone.

The troughs of the castellation arms 38 serve to distribute the second fuel source thoroughly. Accordingly, the second fuel source thoroughly mixes with combustion air in the elongated air inlet device 12.

The burner assembly 10 of the present invention is also provided with staged combustion air.

Returning to a consideration of FIG. 1 as well as a sectional view in FIG. 5, combustion air moves into and through the elongated air inlet device 12 in a direction shown by arrow 44. Combustion air mixes with the first fuel source emanating from the nozzles 24 of the first fuel fingers 26 in the elongated air inlet device 12. Additionally, combustion air mixes with the second fuel source emanating from the troughs of the castellation arms 38. In addition thereto, a portion of combustion air passes through a plurality of tubes or channels 50 which are radially spaced in an annular pattern coaxial with the annular pattern of the first fuel fingers and the castellation arm assembly 36. The tubes or channels 50 may be parallel to the axis of the elongated air inlet device 12 or, in a preferred arrangement, are angled radially outward to produce a conical array.

Combustion air passing into and through the channels 50 exits at the second end 16 of the elongated air inlet device. Accordingly, combustion air is staged to the burner assembly 10.

Whereas, the present invention has been described in relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the spirit and scope of this invention. 

What is claimed is:
 1. A dual fuel, staged air, low NOx gas burner, which burner comprises: an elongated air inlet device having a first open end for introduction of air; a first fuel source conduit delivering a first fuel into said air inlet device; at least one fuel finger in fluid communication with said first fuel source conduit, said fuel finger within said elongated air inlet device; a second fuel source conduit delivering a second fuel into said elongated air inlet device; and a castellation arm assembly in fluid communication with said second fuel source conduit, said castellation arm assembly having a plurality of radially extending castellation arms with troughs therein.
 2. A dual fuel, staged air, low NOx gas burner as set forth in claim 1 wherein said at least one fuel finger includes a plurality of axially aligned fuel fingers spaced in an annular pattern.
 3. A dual fuel, staged air, low NOx gas burner as set forth in claim 2 wherein said plurality of axially aligned fuel fingers are in fluid communication with said first fuel source conduit through a ring manifold to distribute said first fuel from said first fuel source conduit to said plurality of axially aligned fuel fingers.
 4. A dual fuel, staged air, low NOx gas burner as set forth in claim 2 wherein said plurality of axially aligned fingers are juxtaposed between said plurality of radially extending castellation arms.
 5. A dual fuel, staged air, low NOx gas burner as set forth in claim 2 wherein each of said plurality of axially aligned fuel fingers terminates in a nozzle having a pair of ports.
 6. A dual fuel, staged air, low NOx gas burner as set forth in claim 2 wherein said elongated air inlet device is tubular with a center axis and wherein said plurality of axially aligned fuel fingers are arranged in said annular pattern around a center axis coaxial with said air inlet device center axis.
 7. A dual fuel, staged air, low NOx gas burner as set forth in claim 2 wherein said air inlet device has a second end opposed to said first open end.
 8. A dual fuel, staged air, low NOx gas burner as set forth in claim 7 wherein said plurality of axially aligned fuel fingers terminate within said air inlet device spaced from said second end.
 9. A dual fuel, staged air, low NOx gas burner as set forth in claim 2 wherein said plurality of radially extending castellation arms terminate within said air inlet device between said second end and said termination of said axially aligned fuel fingers.
 10. A dual fuel, staged air, low NOx gas burner as set forth in claim 1 including a plurality of staged air conduits, each of said plurality of staged air conduits having a first open end in said air inlet device and a second open end radially outward from said first end.
 11. A dual fuel, staged air, low NOx gas burner as set forth in claim 1 wherein said second fuel source conduit includes a nozzle in advance of said castellation arm assembly.
 12. A dual fuel, staged air, low NOx gas burner as set forth in claim 2 wherein said plurality of axially aligned fuel fingers are equal in number to said plurality of radially extending castellation arms.
 13. A dual fuel, staged air, low NOx gas burner as set forth in claim 2 wherein said first fuel is gaseous.
 14. A dual fuel, staged air, low NOx gas burner as set forth in claim 1 wherein said second fuel is gaseous.
 15. A dual fuel, staged air, low NOx gas burner, which burner comprises: an elongated tubular air inlet device having a first open end for introduction of air and an opposed second end; a first fuel source conduit delivering a first fuel into said air inlet device; a plurality of axially aligned fuel fingers in fluid communication with said first fuel source conduit through a ring manifold, said axially aligned fuel fingers arranged in an annular pattern within said elongated air inlet device wherein said axially aligned fuel fingers terminate with said air inlet device spaced from said second end; a second fuel source conduit delivering a second fuel into said air inlet device; and a castellation arm assembly in fluid communication with said second fuel source conduit, said castellation arm assembly having a plurality of radially extending castellation arms with troughs therein, wherein said plurality of axially aligned fuel fingers are juxtaposed between said plurality of radially extending castellation arms.
 16. A process to produce a low NOx flame from a gas burner, which process comprises the steps of: introducing combustion air into said air inlet device; introducing a first fuel source into an air inlet device through at least one fuel finger within said air inlet device to mix said first fuel source with said combustion air in a controlled manner; and introducing a second fuel source into said air inlet device through a castellation arm assembly having a plurality of radially extending castellation arms with troughs therein, thereby mixing second fuel with combustion air.
 17. A process as set forth in claim 16 wherein said at least one fuel finger includes a plurality of axially aligned fuel fingers spaced in an annular pattern.
 18. A process as set forth in claim 16 including the additional step of introducing combustion air from within said air inlet device through a plurality of staged air conduits, wherein each of said plurality of staged air conduits has a first open end in said air inlet device and a second open end radially outward from said first open end.
 19. A process as set forth in claim 17 wherein said first fuel source is distributed to said plurality of axially aligned fuel fingers through said first fuel source conduit to a ring manifold and thereafter to said plurality of axially aligned fuel fingers.
 20. A process as set forth in claim 17 wherein said plurality of axially aligned fuel fingers are juxtaposed between said plurality of radially extending castellation arms. 